Method of manufacturing grid electrodes



Dec. 26, 1939 w. a. KRAHL.

METHOD OF MANUFACTURING GRID ELECTRODES 3 Sheefs-Sheet 1 Filed Sept. 9, 1937.

j/mfm ATTORN EY W. L. KRAHL METHOD OF MANUFACTURING GRID ELECTRODES Dec. 26, 1939.

Filed Sept. 9, 1937 I5 Sheets-Sh'eet 2 INVENTOR BY% ATTORNE Dec. 26, 1939. w. KRAHL 06 METHOD OF MANUFACTURING GRID ELECTRODES Filed Sept. 9, 1957 a sheets-sheets I T5 [E].

ORNEY Patented Dec. 26, 1939 I 2,l85,l

UNITED STATES P T E T, FFl-CE METHOD OF MANUFACTURING GRID" ELECTRODES 7' Walter L. Krahl, Swampscott. Masa, aseignor to Hygrade Sylvanla Corporation, Salem, Mass" a corporation of Massachusetts Application September 9, 1937, Serial No. 163,001

13 Claims. (Cl. 140-71) This invention relates to methods of making Referring for the present to Figs, 6 and '2, the rid electrodes and more particularly to grid elecgrid electrode according to the invention comtrodes for use in radio tubes and the'like. prises pre e ab y a D parallel up h 01' An object of the invention is to provide a metal side rods l, 2 to which are fastened prefer- 5 method of making a grid electrode wherein each y y w a plurality of grid turns or ii lateral wire or grid turn consists of an individual "laterals 3. In accordance with the invention, length of wire with the ends thereoi fastened to ach t rn is formed from vidual length one of the usual grid side rods, and with the 0f fine wire or ribbon bent or shaped to provide median portion fastened to the other axis side the desired contour to the body p rtion which it rod. As a result of this method or manufacture body portion terminates at opp t n s in subthe grid turns may be disposed parallel to each stflntlally P P rt n While the drawother and with the halves or each turn in the ss ow a grid wherein the y p on s same plana elliptical in shape it will be understood that any a feature of the invention relates to a method t er contour y e vi for e p e. ch

of forming a radio tube grid employing a rotatcular, rectangul r r h k The ends 5, 6 of 15 able mandrel, and whereby the mandrel need be each rn are welded t h i r d while the rotated through an angle of only 180 degrees h p m n P i n 1 i W lded to the side to complete simultaneously all the gridloops or rod 2. If desired, th ff- Portions f e ch turns. As a result of thi feature the grids may grid turn are formed with substantially straight at be made either by hand 'or by automatic maortions 8, 9. i. It By e s n of he e atively at chinery with greater speed and unifor ity, sharp bend between the said straight portions A further feature relates to the novel organid e curved y p the d turns renation and succession of'steps "whereby grid tail! their desired cohtour- Preferably the grid electrodes for radio tubesand th lik ca b turns are fastened to the side rods so that their made in large quantities with maximum unip anes a e p pe di u r to the plane of the side flormity and dimensional accuracy. rods, thus facilitating the shadowing of the mher ieaturesand advantages not specifically turns of one gr with thQSe a Surrounding enumerated will be apparent after a considera=- grid, for P p well-understood in the radio tion of the following detailed descriptions and u e art. f r a pl a embodied in the t p the appended claims. of radio tube designated generally 6L6.

While the method according to the invention Referring to Figs. 1 to 5, the method of formwill be disclosed herein as employing a machine ing the grid of Fl s- 6 and 7 s Substantially as for performing certain operations, it will be obfollows- A p ur y rigid wires l. 2 to convious that grids according to the invention may stitute the side rods, are supported in any suitith be formed entirely by hand or partly by hand able manner on diametrically opposite sides of and partly by machine. Accordingly in the an elliptical mandrel H, or on a mandrel of any drawings, other desired contour. Preferably this mandrel Figs. 1 to 5 are diagrammatic views to illusis formed of two separable halves which are protrate successive steps in forming the grid elecvided with a suitable wedge or thelike, whereby an trode according to the invention. the mandrel may be expanded and collapsed to do Fig. 6 is a plan view of a grid electrode accord- Pe it th S p and removal of the finished ing to the invention. grid. A plurality of wires or ribbons l2 (Fig. 9)

Fig. 7 is an elevational view of the grid elecfrom a corresponding plurality of pay-oil reels trode of Fig. 6. l3 have their ends welded as indicated by nu- Fig. 8 is a top plan view partly in section, of a meral M, to the upper i'ace of side rod 2 (Fig. 1). 45 machine which may be utilized in practising the Preferably, these wires are guided through a invention. comb l5 (Fig. 9) whereby they are maintained Fig. 9 is an enlarged detail view of part of the parallel to one another and are space'dapart the machine of Fig. 8. required distance. The next step is to weld each so Fig. 10 is a cross sectional view of Fig. 8 taken wire l2 to the side rod I, as indicated by the along the line ill-l0 thereof. numeral l8 (Fig. 2), taking care that the wires Fig. 11 is a detail sectional view 01 Fig. 10 are held under sufllcient tension to conform them taken along the line ll-ll thereof. to the periphery of the mandrel. The mandrel N Fig. 1215 a cross sectional view of Fig. 10 taken is then rotated around its axis in the direction as along the line lZ-l2 thereof. of the arrow (Fig. 2) thus bringing the side rod 2 flit into the position previously occupied by side rod i, as indicated in Fig. 3. The wires I2 are then welded to the side rod 2 as indicated by the numeral I 8. Preferably instead of employing a single mandrel, a pair of spaced mandrels l1 and 69 are employed, so that at the same time the grid wires are welded to the side rod l on mandrel N (Fig. 3) they can be simultaneously welded to the side rod 2 which has been previously loaded into the mandrel l9. At this stage of the process the grid wires are therefore completely looped around the grid side rods I, 2 on mandrel i1 and are fastened to the side rods l and 2 as well as to the side rod l on the next mandrel.

The next step is the severing of the grid wires between the two mandrels as indicated diagrammatically by the cutting members 20, 2| (Fig. 4). Preferably, the cutting edges are designed so that the grid wires are severed as close as possible to the respective side rods. The mandrel l1 with the completely formed grid therein is next expanded against a suitable die whereby the grid loops are formed to the desired contour, such for example as illustrated in enlarged form in Fig. 6. While the grid on mandrel I1 is being formed, the next mandrel I9 of the pair ismoved to the position previously occupied by mandrel I1 and the wires ii are welded to the side rod 2 as indicated by the numeral 22 (Fig. 4). Thereafter the mandrel I9 is rotated through an angle of 180 degrees to the position shown in Fig. 5 whereupon the wires l2 are welded to the side rod 2 as indicated by the numeral 23. The grid on mandrel i9 is then expanded and shaped as already described for mandrel I 1. After the formation and shaping of the grids as described, the mandrels are collapsed by removing for example the wedge 26, whereupon the grids may be easily removed.

From the foregoing description, it will be seen that the grids are formed merely by rotating each mandrel through an angle of 180 degrees, and the various grid wires or laterals are all simultaneously fastened to the respective side rods and are simultaneously formed around the respective mandrels, thus insuring accuracy of spacing between the various wires and expediting the formation of the finished grids. Furthermore, each grid wire is fastened intermediate its ends by means of. an offset portion, to one side rod and the ends of each turn are fastened at opposite sides of the other side rod, thus enabling the grid wires to be properly shaped and to retain their shaped form since the offset portions of each grid wire'are conformed to the periphery of the side rods.

Referring to Figs. 8, 9, 10 and 11 a description will now 'be given of the more important parts of a typical mechanism for forming the grids of Figs. 6 and '7. The machine comprises a main horizontal shaft 63 carrying a circular plate 4| and to which is attached a drum 35. Plate 4| is adapted to be rotated in a step-by-step manner by any suitable means to twelve different positions, for example by a Geneva movement including a revolving pin 30 and cooperating slots'30 in plate M. Supported in drum 35 and for individual rotation are twelve grid mandrels designated A to L consecutively. In order to simplify the description, it will be assumed that the position in which mandrel A is shown in Fig. 8 is position #1, mandrel B is position #2 and likewise for the remaining mandrels. As shown in detail in Fig. 10, each mandrel is split t u out its length so as to enable a wedge 24 to be inserted between the halves of the mandrel for the purpose of expanding the grid turns formed thereon as described hereinbelow. Normally, that is with the wedge withdrawn, the mandrel halves lie flat against each other so that their combined outer peripheries provide the proper contour for the grid turns to be formed thereon. As shown more clearly in Figs. 8 and 11, each mandrel is provided on opposite diameters with a pair of longitudinal grooves to receive the grid side rods. In order to prevent the mandrels sliding in the drum 35 in a direction parallel to their major axes each is provided with a pair of plates 39, 43 which fit in'a peripheral groove around the end of the mandrel as shown in Fig. 10. Each mandrel is designed to be rotated around its major axis when the mandrel reaches the proper position in the indexing movement of the drum 35, and in order to prevent acci dental rotation at other positions, each mandrel is provided at the bearing end portions 33, 34 with depressions which'register. with the balls 31 spring-pressed by springs 33' (Figs. 10 and 11) The ends 33, 3d of each mandrel are slightly larger in cross section than the winding portion M-M of the mandrel, and are preferably equal to the major axis of the finished grid. The grooves in the mandrel which receive the grid side rods are of different depth along the mandrel length. For example the depth of each groove between the points M-M is such as to; surround less than 180 degrees of the side rod periphery so that more than one half of the side rod periphery protrudes above the surface of the mandrel." The portion of the mandrel grooves between the point 'M' and the upper end of the grooves is gradually deepened so that at this portion the grooves surround practically the entire periphery of the side rods, thus. providing a chuck" hold on the side rods, at their upper ends (Fig. 10). Thus when the side rods are loaded into the mandrels they; are clamped between the portions 33, 35..

Referring ,to Figs. 8 and 10, the drum .35 has twelve slots 36 in its surface, one for each'mandrel, each slot having a width equal to the width of the major diameter of the associated mandrel, and the inner end of each slot being semi-circular to correspond with the curvature of the mandrel ends 33, 34. 'Slidably mounted in each slot is a plate 2| normally held against the bearing portions 33, -34. of the mandrel by a stationary ring The slidable plates 2| are semi-circularly concave at their inner ends to conform to the curvature of the bearing ends- 33, 34 of the mandrel. Thus one half of the bearing for each mandrel is provided by an associated slide M and the other half is provided by the cooperating semi-circular cut-out in drum 35.

Referring more particularly to Fig. 8, the drum with its mandrels is arranged to form simultaneously, two sets of grids, thus while one set is being formed on mandrels A to F, a second set. is being formed on mandrels G to L; This allows grids of different numbers of turns or grids of different pitches to be formed "on the same machine. For this purpose, there are mounted adjacent the drum 35 two series of pay-off reels l3, the wires l2 from which are guided by a comb or a grooved roller l5 attached by a suitable bracket to ring 20 When the drum is in the position shown in Fig. 8, the side rods I and 2 are guided or placed in the adjacent grooves in mandrels B and A. Since any well-known wire feeding and guiding means may be employed for loading the side rods into the mandrel grooves detailed description thereof is not necessary; Likewise after the side rods are loaded into the mandrel grooves they are cut to the proper length by any well-known cutting mechanism (not shown). If desired suitable springs (not shown) may bear against the side rods to hold them in the mandrel grooves against accidental sliding movement along the mandrel.

When the side rods I and 2 have been loaded into the mandrels inposition #1, the drum is indexed one step in the direction of the arrow by members 30, 3| (Fig. 10), thus bringing the previously loaded mandrels B and A into position #2. In this second position, the wire strands l2 from reels l3 are fed through the guides l5 and are welded to side rod 2 by means of welding jaws i8 and;22 which are closed on to side rod 2 by any suitable operating ,mechanism such as a, sliding wedge pr the like (not shown). In the meantime of course another set of side rods I, 2 have been loaded into'the mandrels .A and L as above described for mandrels B and A. In starting the machine, the wire strands l2 may be fastened'to the side rod I that happens to be in the position of mandrel C, but when the machine is started in operation the fastening to the side rods 2 on successive mandrels will be eiiected automatically. The drum is next indexedto its third position to bring the mandrel B carrying side rods i and 2, into the position previously occupied by mandrel C. In this position the welding jaws i8 and 23 are closed against side rod i thus welding the strands i 2 thereto. It will be noted that by reason of the angle at which the wire strands are fed to the mandrels and by reason of the rotation of the drum, as the mandrel is moved from position #2 to position #3 the strands are under sufficient tension to conform them closely to the contour of one half of the mandrel.

When the Welding of the wire strands on side rod l is completed, the jaws l8 and 23 are retracted'. Preferably, however, jaw. i8 is moved back to its normal position as shown in Fig. 8, but jaw 23 is .moved back only sufficiently to clear the side rods on the mandrel in position #3 when the latter is rotated about its longitudinal vaxis in' thedirection of the arrow as will now be described. For this latter purpose, there is provided a bushing s2 which is slidably keyed onshaft 42 and is adapted to be raised and lowered on said shaft at the proper interval by means of an operating arm 42. Shaft ,42 is arranged to be rotated through an angle of degrees at the proper time with relation to the indexing movement of the drum 35, by any well-known means, for example'bya-gear 42 and a cooperating segmental gear.42 the latter being, moved into engagement with gear 42 when themandrel reaches position #3 and after the bushing 42 has been coupled to the end oi the mandrel as shown in- Fig. 10. Preferably as shown in Fig. 12 the wall of the bushing 42 is provided with diametrically opposite grooves to accommodate the side rods I and 2. 1

,After the jaws I8 and 23 are retracted, the

arm 42 is operated to couple the mandrel to the shaft 42 whereby the mandrel is rotated about its longitudinal axis through an angle of 180 degrees, whereupon the shaft 42 is uncoupled from the mandrel. By suitable timing cams or the 7 like (not shown), the jaws 23 and I8 are again suitable timing cam (not shown).

closed to weld the strands l2 to the side rod 2 at the points l8 (Fig. 3). At this time also the jaws l8 and 22 are closed upon the side rod 2 of the next succeeding grid which is now in position #2.

The drum 35 is next indexed to bring the completely welded grid into position #4, whereupon the sliding members 24, 26 and 21 are moved to clamp the adjacent side rods of the grids on adjacent mandrels C and D. For this purpose, it will be noted that the member 21 is provided with spaced clamping jaws 21 21* which cooperate with the corresponding clamping edges of members 24 and 26. It will also be noted that the faces of members 24 and 26 as well as the faces of members 22 and 23 are curved to correspond with the curvature of the mandrel. While the side rods are clamped by members Ti -24 and 2l -26, the cutter 25 is forced between the two adjacent clamped side rods on mandrels C and D i to sever the completely formed grid on mandrel D from the half-formed grid on mandrel C.

Drum 35 is next indexed to position #5 where the Wedge 24 (Fig. 10) is inserted between the two halves of the mandrel under control of a In this position of the drum, as well as in positions 2, 3 and 4, the stationary ring 20 is cut away so that the sliding members 2| can move radially away from the center of the drum, thus permitting the mandrel to expand upon the insertion of wedge 24: The sliding sections 2| 8 when they register with the cutout section of ring 2i) are held resiliently in place by means of the ring sections 3| which are normally disposed so that the high par of the curved inner face 3| extends inwardly i Corresponding members to *member 3| are pro vided in positions B, C and D so' that when t e welding electrodes I 8 22**23 and the clamping jaws Zi -21 24 25 engage the respective grid side rods the mandrels are capable of moving radially away from the center of the drum through a small distance, thus rigidly clamping the side rods during the welding and cutting operations.

After the wedge 24 has been inserted between A'spring 29 bears against the member 3| I the two halves of the mandrel in position #5,

and after it has been removed, the mandrel contracts, but the wire strands have been given a, permanent set and have been stretched so that the,

grid turns are slightly larger than the mandrel. The drum is then indexed to position #6 wherein a pair of pincer-like jaws (not shown) grasp the finished grid side rods which extend beyond the end of the mandrel, whereupon the jaws are 'retracted to strip the grid from its mandrel. The finished grid is then dropped into a suitable conveyor or container.

When the drum reaches position #7, side rods are inserted and cut to length exactly as described in connection with mandrels A and B (positions 1 and 2), and the foregoing cycle of operations of winding, welding, severing and expanding the grid turns, and the stripping of the finished grid from its mandrel is repeated in positions 7 to 12 inclusive. The grids formed in positions '7 to 12 may have diiferent strand spacings, or different strands pitches or gauges fro m those being formed in positions 1 to 6, thus allowing grids of different mechanical and electrical characteristics to be made on the same machine. Preferably the machine is so designed that when the man drels are mounted in a circle as shown, the adjacent grid side rods on adjacent mandrels' are so close together, that it is merely necessary to shear the strands l2 once between the mandrels, rather than to separate the mandrels and re-v quiring the cutting of the strands twice between adjacentside rods.

What I claim is:

1. The method of forming a grid electrode for an electric discharge tube which comprises supporting a pair of grid side rods on a mandrel, fastening simultaneously a plurality of grid strands to one of the side rods, conforming the fastened strands around one side of the mandrel, fastening said strands to the other side rod, rotating the mandrelwith the fastened strands, and then fastening said strands to the first-mentioned side rod.

2. The method of forming a grid electrode for i an electric discharge tube which comprises supporting a pair of grid side rods on a mandrel, supporting a plurality of grid strands in substantially the same plane and transversely to said side rods, conforming the strands around one half of the mandrel, fastening-the strands to the first side rod and to the second side rod, rotating the mandrel with the fastened strands around the mandrel axis, and then fastening the strands to the first side rod.

3. The method of forming :a. grid for an electrode discharge tube which comprises supporting a pair of grid side rods on opposite sides of a mandrel, fastening a plurality of grid strands to one of said sid rods, moving the mandrel bodily with the fastened strands and then fastening the strands to the other side rod, rotating the mandrel with the fastened turns in a direction so as to wrap the fastened strands around the mandrel and then fastening the strands to said one of said side rods.

a. The method according to claim 1 in which the strands are severed adjacent the first side rod after the third fastening operation.

5. The method of forming a grid for an electric discharge tube which comprises supporting a pair of grid side rods on a mandrel, fastening simultaneously a plurality of grid strands to the first side rod, bending saidstrands around one half of the mandrel without ;rotating the mandrel about its own axis, fastening the strands to the second side rod, rotating the mandrel with the fastened turns through an angle of 180 degrees, and then fastening said strands to said first side 6. The method of forming a grid for an electron v discharge tube whichcomprises, supporting a pair of grid side rodson a mandreLwelding a plurality wires from .a plurality of pay-.offreels to the st side rod, revolving said mandrel and side is about a central axis in a direction to unreel edetermined lengths of wire from said reels, conforming said lengths to one half of the mandrei, welding said wires to the second side rod,

rotating the mandrel around its own axis, and

welding said wires to said first side rod.

7. The method of forming a grid for an electron discharge tube which comprises, supporting a pair of grid side rods on a mandrel, supporting another-pair of grid side rods on a second mandrel,

ffast'en'inga plurality of grid strands to the first side-rod of the first pair of side rods, fastening the strands to the-second side rod of the first pair-of side rods -"rotating the l mandrel and the first pairjof side rods through an'angle-of 180 degrees; fastening said strands to the first side rod of the first'pairand tothe first side rod of the secondr p'air, and then {severing the strands between thefirst side rod'of the first pair and the first side-rodiofthe second pair.

8. The method of forming a grid electrode for an j electric dischargetube which comprises, fastening a plurality of substantially parallel grid strands simultaneously to a first grid side rod, fasteningsaid strands simultaneouslyto a second grid side rod, rotating the side rods about their common axis to bring the first side rod into the position previously occupied by the second side rodgfastening the strands simultaneously to said first side rod, and expanding the portions of the strands :between .the'side rods to form individual grid loops." 1 r 9. The method jaccordlng lto' claim 8 in which thestrandsare expanded against a pair of channeled members while the side rods are clamped between the said members. -1 7 10. The methodof 'making a grid electrode which includes the steps of supporting a plurality of pairs ofgrid-side rods-Jon aflpairof adjacent spaced mandrels, welding. ag -plura'lity of grid strands to the first side rod on the, first mandrel, moving the first mandrel with the welded strands bodily at anangleto the strands to shape the strands around one. half of 'the first: mandrel, weldingth'e strands 'to the second side rod on the first mandrel, rotating. the first mandrelaabout its own longitudinal axis through an angle of 180 degreestc shape the strands-.aroundthe other half of the first mandreL'weldIng saidstrands tosaid first side rod. and'alsowelding said strands to the first side rod on the second; mandrel, and severing the strands between the adjacent ,side rods on the two mandrels.

11. The method according t6 claim 10 n which,

the second welding of the strands to the first side rod on the first mandrel is efiectedjon the oppoe rod from that where the strands are shaped to provide substantially U-shaped extensions where they surround theside rods.

' WALTER L. 3am. 

